1. Field of the Invention
The present invention relates to a liquid for a liquid lens. More specifically, the present invention relates to silicone oil having a specific structure used for an insulating solution for a liquid lens and an insulating solution comprising the silicone oil.
2. Description of the Related Art
In recent years, rapid growth in mobile communication apparatus and computer technology as well as consumers' diverse needs have brought about fierce international competition for technology improvements to realize lenses with auto focus (A/F) and optical zoom. As general methods to obtain lenses with auto focus (A/F) and optical zoom, there may be used mechanical movement of a lens, variation in curvature of a lens and changes in physical properties of a lens. In the case of general multi-focus optical lenses commercialized in digital cameras, etc., the distance between a plurality of lenses having a predetermined refractive index must be mechanically varied, thus involving disadvantageously high costs and taking up much space. Accordingly, most cameras in notebooks and cellular phones having strict restrictions on volume are being provided with lenses incapable of automatic focusing.
Liquid lens is a new technology that realizes auto focus (A/F) and optical zoom functions by variation in curvature thereof based on the electrowetting phenomenon. Liquid lenses are usable as a micro-optical zoom lens for a variety of cameras and mobile communication apparatus, etc., owing to reduced consumption power and minimized volume. In addition, liquid lenses are widely utilized in a variety of applications, including computer components and optical devices.
An insulating solution must have chemical stability and be stably operated in operational and conservative temperature ranges. The insulating solution must have the similar density and viscosity to those of a conductive electrolyte solution to ensure an easy operation upon application of a voltage and maintain an interface between the insulating solution and the electrolyte solution.
As the difference in surface tension between the two solutions increases and the difference in refractive index between the two solutions decreases, stability at the interface between the solutions and device performance tend to improve.
Although a number of patent applications associated with conventional liquid lenses describe a use of a silicone oil as an insulating solution for a liquid lens, they fail to specifically disclose the insulating solution suitable for use in a liquid lens. Accordingly, general silicone oils are currently being used as an insulating solution for a liquid lens.
However, general silicone oils do not satisfy the requirements, i.e., density, refractive index and viscosity conditions, for an insulating solution for a liquid lens. Accordingly, to satisfy these requirements, a mixture of an excess organic additive and such a silicone oil is being currently used.
As a result of repeated eager studies, the inventors found that when the organic additive is used in an excessive amount, it has a strong tendency to adhere to the inner surface of a hydrophilic liquid lens due to its hydrophilicity, thus having a variety of bad effects on operation of the liquid lens, e.g., insufficient operation. Accordingly, the inventors confirmed that the organic additive must be used in a minimum amount.